1. Field of the Invention
The present invention relates to an ink jet printer that conducts printing while reciprocating a print head, and more particularly to an ink jet printer in which a printing positional deviation of return-printing with respect to go-printing is automatically corrected.
2. Description of the Related Art
Various ink jet printers have been put in practical use in which color printing is generally conducted on a sheet in such a manner that a print head having a large number of ink jet nozzles jet out ink supplied from ink cartridges into ink droplets bit by bit. To increase the printing speed, ink jet printers called “bidirectional printing” have been put in practical use which not only conducts go-printing (go-direction printing) while moving the print head in a forward direction, but also conducts return-printing (return-direction printing) while moving the print head in a backward direction.
In ink jet printers that can bidirectionally print, a printing positional deviation tends to occur between go-printing and return-printing because of the following factors: backlash exists in a carriage driving mechanism during each of a go-direction movement and a return-direction movement; a positional deviation exists between a go-printing position at which ink jetted during go-printing adheres to a sheet and a return-printing position at which ink jetted during return-printing adheres to the sheet; and a go-printing speed and a return-printing speed slightly differs from each other. Various proposals have been made to prevent such a printing positional deviation.
For example, in a serial printer disclosed in JP-A-10-329380, a number-of-correction-steps table is stored in advance in which line numbers (1, 2, 3, . . . , 9, 0) and the numbers of correction steps in return-printing correlate with each other. When printing position correction processing is executed, a line number, a vertical ruled-line pattern of go-printing, and a vertical ruled-line pattern of return-printing are printed on the same line for each line number. An inspector or a user determines, by a visual check, a vertical ruled-line pattern having a smallest printing positional deviation, and sets the corresponding line number as deviation correction data for printing control by inputting the line number to the serial printer.
In a printing apparatus disclosed in JP-A-10-6533, every time the head cartridge of an ink jet recording apparatus is replaced, plural kinds of test patterns are printed while the ink jetting timing conditions change between go-printing and return-printing in different manners. The plural kinds of printed test patterns are read by scanning those test patterns by an optical reading means provided in the recording apparatus, and an optimum test pattern that is closest to a proper image pattern that is free of deviations is automatically determined. The ink jet recording apparatus itself automatically sets the optimum test pattern as corresponding to the best jetting timing conditions.
As described above, in the serial printer disclosed in JP-A-10-329380, the inspector or the user determines a vertical ruled-line pattern having a smallest printing positional deviation on the basis of a vertical ruled-line pattern of go-printing and a vertical ruled-line pattern of return-printing that are printed on the same line for each line number, and manually sets the corresponding line number as deviation correction data for printing control. This raises various problems. For example, the correcting manipulations for the printing positional deviation correction becomes complex. Where there are a plurality of line numbers among which a line number for printing positional deviation correction is to be selected, an error likely occurs in setting a line number corresponding to the best pattern.
In the printing apparatus disclosed in JP-A-10-6533, plural kinds of test patterns are printed while the ink jetting timing conditions change between go-printing and return-printing in different manners. An optimum test pattern can be determined and set automatically by scanning those test patterns by the reading means. However, there remain several problems. For example, an inspector cannot recognize which is the optimum test pattern that has been set automatically, and cannot visually check whether the test pattern that has been determined to be the best test pattern is really the best one.